PROJECT SUMMARY/ABSTRACT Millions of patients suffer from delayed wound healing stem from systemic diseases or external traumas, which can result in a loss of skin integrity, disability, and even death. An important aspect of healing is re- epithelialization that entails both proliferation and migration of keratinocytes at the periphery of the wound. When re-epithelialization is not achieved in a timely fashion, patients suffer from delayed wound healing. Understanding the role and function of keratinocytes in re-epithelialization will be of benefit to these patients. Oral wounds exhibit accelerated re-epithelialization when compared to equivalently sized skin wounds. Our laboratory recently identified a previously unnoticed landscape of non-coding RNA in saliva. Of particularly interests are three distinctive oral-piwi-interacting RNAs (oral-piRNAs) that are uniquely present in saliva and oral keratinocytes and appear to contribute to the oral wound re-epitheliazation phenotype. The applicant performed studies including in vitro scratch assays that demonstrated a continual increase of oral-piRNA expressions post wounding in human oral keratinocyte and not in skin keratinocytes. Furthermore, independent knockdown of these oral- piRNAs in the human oral wound scratch assay resulted in the significant delay and failure of oral wound closure. The overarching hypothesis of this proposal is that oral-piRNAs are intrinsic factors in human oral keratinocytes modulating the rapidity of wound closure. Based on the preliminary data, the applicant aims to validate the role of oral-piRNAs in oral wound healing in a 3D ex-vivo oral mucosal wound healing model in Aim 1 and then follow by elucidating the cellular and genetic factors responsible for the oral-piRNA mediated oral wound healing phenotypes, including epithelial migration and proliferation in Aim 2. By understanding oral-piRNA roles in normal oral wound healing, we can identify differences in skin wound healing regulation and alterations in delayed healing wounds. As we unravel how oral-piRNAs modulate human oral keratinocyte proliferation and migration, we may improve wound healing therapeutic developments. The long-term goals of this proposal are to advance the biological understanding and functions of piRNA relevant to human oral health and diseases and use the findings to benefit wound healing in patients. This F30 fellowship will prepare the trainee for an academic career to become an independent researcher in oral wound healing and piwi-interacting RNA biology.